Vehicle fuel systems include evaporative emission control systems designed to reduce the release of fuel vapors to the atmosphere. For example, vaporized hydrocarbons (HCs) from a fuel tank may be stored in a fuel vapor canister packed with an adsorbent which adsorbs and stores the vapors. At a later time, when the engine is in operation in a hybrid vehicle, the evaporative emission control system allows the vapors to be purged into the engine intake manifold for use as fuel.
The fuel vapor canister in the hybrid vehicle may primarily store refueling vapors. Further, vapors from running loss and diurnal temperature cycles may not be transferred into the fuel vapor canister and may be contained within the fuel tank. Accordingly, pressure may build in the fuel tank and a higher pressure may exist within the fuel tank. When a vehicle operator indicates a demand to refuel the hybrid vehicle, the fuel cap may be locked until venting of the fuel tank is allowed to sufficiently reduce tank pressure. As such, the fuel cap may be unlocked only after the tank pressure is below a threshold pressure protecting the vehicle operator from being sprayed with fuel vapor.
Previously disclosed systems include a single fuel tank isolation valve (FTIV) between the fuel tank and the fuel vapor canister. The FTIV may be a solenoid valve that is normally closed but the FTIV may be opened to prepare the fuel tank for refueling. However, a constant voltage supply may be provided to energize the FTIV to open and enable depressurization of the fuel tank. As such, the constant supply of voltage to the FTIV may increase power consumption and lead to a rise in maintenance costs. Accordingly, the FTIV may be replaced with a latchable refueling valve. The latchable refueling valve may reduce power consumption but may not provide a sufficient depressurization rate during certain conditions. For example, in hot weather conditions, the fuel tank may be at a higher pressure and depressurization via the latchable refueling valve may take a longer time. Specifically, the vehicle operator may have to wait for a longer time until the fuel tank is ready for refueling.
The inventors herein have recognized the above issues, and have identified an approach to at least partly address the issues. In one example approach, a method comprises adjusting a latchable valve to a first, latched position via a voltage pulse, the first, latched position enabling a depressurization of a fuel tank, and responsive to a pressure in the fuel tank higher than a first pressure threshold after a pre-determined duration, moving the latchable valve to a second, unlatched position with a more continuously applied voltage, the second, unlatched position more open than the first latched position. In this way, the fuel tank may be depressurized at a faster rate.
In another example, a system for a hybrid-electric vehicle comprises an engine, a fuel tank coupled to a fuel vapor canister via each of a first conduit and a second conduit, a tank pressure control valve coupled in the first conduit between the fuel tank and the fuel vapor canister, a latchable refueling valve coupled in the second conduit between the fuel tank and the fuel vapor canister, the latchable refueling valve including a latch and a latch guide, and a controller configured with instructions stored in non-transitory memory and executable by a processor for, in response to a refueling request, opening the tank pressure control valve while maintaining the latchable refueling valve closed at a latched, closed position, and when fuel tank pressure is lower than a first pressure threshold, actuating the latchable refueling valve with a voltage pulse to a latched open position to transfer fuel vapors into the fuel vapor canister, and if fuel tank pressure is higher than a second pressure threshold after a pre-determined duration, actuating the latchable refueling valve to an unlatched open position with a more continuously applied voltage, for example more continuously applied than an intermittent pulse to move the valve to a different position. In one example, the more continuously applied voltage may be a continuous voltage maintained at a maximum voltage level continuously over a duration that is longer than a maximum duration used to move the valve from one position to another. In this way, higher tank pressures can be released prior to fuel tank refueling in a faster and safer manner.
For example, a hybrid vehicle may include a fuel tank coupled to a fuel vapor canister via a first conduit and a second conduit. A tank pressure control valve may be coupled within the first conduit while a latchable refueling valve may be coupled within the second conduit. The tank pressure control valve and the latchable refueling valve may be normally closed such that fluidic communication between the fuel tank and the fuel vapor canister is impeded. Upon a refuel request by a vehicle operator, the tank pressure control valve may be opened first, while maintaining the latchable refueling valve in its latched closed position. After tank pressure falls below a first pressure threshold, the latchable refueling valve may then be adjusted from the latched closed position to a latched open position via a pulse of voltage. The latched open position of the latchable refueling valve may enable fluidic communication between the fuel tank and the fuel vapor canister. Further, fuel vapors from the fuel tank may be transferred to the fuel vapor canister via the latchable refueling valve at a first flow rate. After a pre-determined duration at the latched open position, if fuel tank pressure remains higher than a second pressure threshold, the latchable refueling valve may be adjusted to an unlatched open position. As such, the latchable refueling valve may receive a continuous supply of voltage when in the unlatched open position. Further, the unlatched open position of the latchable refueling valve may enable a higher flow rate of the fuel vapors from the fuel tank to the fuel vapor canister.
In this way, a technical effect of a faster depressurization rate of the fuel tank may be achieved. The unlatched open position of the latchable refueling valve may provide a more open position of the latchable refueling valve allowing an expedited release of fuel vapors from the fuel tank into the fuel vapor canister. Further, since the latchable refueling valve is adjusted to the unlatched open position only after the pre-determined duration, the latchable refueling valve may not receive continuous voltage through the entire duration of depressurization of the fuel tank. Accordingly, power consumption may be reduced and cost savings may be attained. As such, a balance between reduced power consumption and a faster depressurization may be obtained. Overall, waiting time for initiating refueling may be reduced while ensuring the vehicle operator is protected from fuel vapor spray.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.